Patent Documents 1 and 2 disclose synthetic resin containers of rectangular parallelepiped shape. The containers have an opening to be closed by a metal cap (“metal cap opening”) formed at least near an end of their top face and three handgrips disposed parallel to each other along the (longer) sides of the top face. When two of these containers are joined so that their handgrips become parallel to one another, those handgrips which are placed far out on each container are closely positioned, which enables one to hold both of those handgrips at a time. By placing fingers under the handgrips, one can carry two containers by one hand and a maximum of four containers by both hands at a time.
If the container becomes heavy as more contents are put in the container, two persons can hold the handgrips on the two sides of the top face of the container by reaching for them from the respective sides to cooperate and carry a single container.
Patent Documents 1 and 2 do not disclose a manufacturing method for these containers. Patent Document 3 is conventionally known to disclose a manufacturing method for a container with a single handgrip.
Patent Document 3 discloses a container manufacturing method that includes placing a parison in a pair of dies composed of a cavity for molding a container main portion including a metal cap opening and a cavity for molding a handgrip portion, clamping the pair of dies, and subsequently blowing air into the parison. This method molds both the container main portion and the handgrip portion simultaneously in a single die by blow molding.